Research Objective
Global climate change generates even higher demands on the quick release of new varieties, while Doubled Haploids (DHs) can significantly reduce the time for breeders to speed up the development of new varieties. Instead of five to six generations to have new traits fixed, the DH method only needs one generation. The wide range of applications of DHs and the advantages of employing DH technology benefit the industries when DH technologies are available, such as in the canola and corn industries. However, pulse crops are generally considered recalcitrant toward the technology, and no efficient DH protocol is available for any of the pulse crops. Epigenetic regulation is involved in diverse growth and developmental processes, including somatic embryogenesis and plant regeneration. DH production through microspore culture is a broadly used method for crop species as compared to other methods. Supplementing epigenetic chemicals into the culture has shown increased DH induction in cereal crops and Brassicas from the research done at the NRC and other research groups. NRC’s recent work also showed beneficial effects of epigenetic chemicals in DH induction in peas. Therefore, in this proof-of-concept project, we evaluated six different pulse species (lentil, chickpea, faba bean, dry bean, soybean, and fenugreek) for their DH induction responses towards epigenetic chemicals, using pea as a control. The knowledge and insights gained from this project will help formulate a more targeted approach to DH technology development in pulse crops.
Where and how was the research conducted?
Plants were grown in growth cabinets and lab studies were conducted in Saskatoon, SK.
Why?
Epigenetic chemicals benefit DH induction in other species, such as wheat, barley, and Brassicas, as well as pea from NRC’s in-house study. Pulse crops are recalcitrant to DH technology, therefore, we aimed to understand if epigenetic chemicals would promote DH induction responses in six difference pulse species.
Objective: Evaluate six pulse species on their DH induction responses towards three epigenetic chemicals using field pea as a control.
Through this proof-of-concept project, callus with embryo-like structures developed from chickpea after being transferred to regeneration media, faster than the field pea control. In addition, microspore divisions were observed in faba bean, while swollen microspores were observed in all the other pulse crops tested including lentil, fenugreek, soybean and dry bean, after the epigenetic chemical treatment. Epigenetic chemicals had a positive effect on DH induction in pulse crops, though induction responses are species and genotype dependent with interactions among genotypes and epigenetic chemicals.
What are the results of this project in more detail?
Our results showed epigenetic chemicals had a positive effect on promoting multicellular structures and callus development from microspores in pulse crops. Overall all seven pulse crops, including the control field pea, showed swollen microspores after epigenetic treatments, which were considered the first visual appearance once induced. In addition, three pulse crops including field pea, chickpea, and faba bean showed subsequent development in microspore division. Furthermore, multicellular structures developed in pea and chickpea. Utilizing the callus regeneration medium we developed and tested in pea at NRC, embryo-like structures quickly developed from microspore-derived calli in chickpea. The effects of epigenetic chemical treatment on microspore induction were significant and species-dependent. This is in line with our earlier study in wheat showing different induction effects from different epigenetic chemicals.
As in any other tissue culture system, DH induction through microspore culture is affected by many factors, including before the microspores are extracted. The genotype effect is usually the dominant one among other preextraction factors. As shown from the results, the effects of genotypes/cultivars on microspore induction were significant with certain genotypes showing better induction than others. Our results further showed genotype differences within pulse species existed toward the DH induction responses from epigenetic chemicals and these genotypes could be utilized in further DH technology development for respective pulse species. An ANOVA (Analysis of Variance) test also showed significant interactions between cultivars, epigenetic treatment, and culture time. The significance of culture time in the induction responses across all tested pulse species indicates developmental shifts either positively towards further developing multicellular structures, or negatively towards not sustaining the induction responses. Negative responses across the culture period could signal a shift in nutrient requirements after the microspore induction phase. In the current proof-of-concept project, we aimed to evaluate the effects of epigenetic chemical treatment on DH induction in different pulse crops. Further in-depth studies will be needed to optimize the nutrient requirements to sustain the development of induced microspores.
What benefit will these outcomes bring to farmers in SK?
This proof-of-concept project showed epigenetic chemicals were beneficial in DH induction of pulse crops, and the effects were species-dependent with the interaction between genotypes and epigenetic chemicals. The positive responses and even advanced development of microspores in pulse crops such as pea, chickpea, and faba bean warrant further discussions with breeders, industry, and funders to leverage the knowledge gained from this project for a more targeted approach to DH technology development in pulse crops. Establishing speed-breeding DH technology for pulse crops would allow breeders to rapidly develop new cultivars with desirable traits such as increased yield, biotic/abiotic stress tolerance, and improved quality. When facing various challenges posed by climate change, including increasing adverse environments and emerging diseases and pests, accelerating cultivar development of Canadian pulse crops will be essential to maintain the competitiveness of Canadian pulses and improve the sustainability of the pulse industry.